Antidepressant efficacy of high-frequency transcranial magnetic stimulation over the left dorsolateral prefrontal cortex in double-blind sham-controlled designs: a meta-analysis

Background For more than a decade high-frequency repetitive transcranial magnetic stimulation (rTMS) has been applied to the left dorsolateral prefrontal cortex (DLPFC) in search of an alternative treatment for depression. The aim of this study was to provide an update on its clinical efficacy by performing a meta-analysis involving double-blind sham-controlled studies. Method A literature search was conducted in the databases PubMed and Web of Science in the period between January 1980 and November 2007 with the search terms ‘depression’ and ‘transcranial magnetic stimulation’. Thirty double-blind sham-controlled parallel studies with 1164 patients comparing the percentage change in depression scores from baseline to endpoint of active versus sham treatment were included. A random effects meta-analysis was performed to investigate the clinical efficacy of fast-frequency rTMS over the left DLPFC in depression. Results The test for heterogeneity was not significant (QT=30.46, p=0.39). A significant overall weighted mean effect size, d=0.39 [95% confidence interval (CI) 0.25–0.54], for active treatment was observed (z=6.52, p<0.0001). Medication resistance and intensity of rTMS did not play a role in the effect size. Conclusions These findings show that high-frequency rTMS over the left DLPFC is superior to sham in the treatment of depression. The effect size is robust and comparable to at least a subset of commercially available antidepressant drug agents. Current limitations and future prospects are discussed.